Medium frequency induction furnace will be a variety of problems in the course inevitable, the life lining material is one of the greatest concerns. For the melting department, it is extremely important to analyze the factors affecting the life of the intermediate frequency induction furnace lining.
Analysis of Main Factors and Countermeasures
1. Furnace Construction Process
The quality of the lining knot directly affects service life. The knotting quality of the lining is related to the sintering quality, and the sintering quality affects the performance. When the lining is knotted, the sand material maintains a uniform particle size, and the coarse and fine particles do not cause segregation. When the material is added, the layer and the layer are tightly combined, and the density of the lining after the knotting is high, and the strength of the sintered layer after sintering is high. The tendency of the furnace wall to crack is relatively small. If the furnace lining is knotted, the vibration will be unreal, which will result in the furnace lining not being dense or partially loose. When the metal liquid pressure is high, leakage may occur. After finishing the layering by hand, the surface is not loosened and the feeding will cause delamination. Lateral cracks will occur during use, and the crack cannot be bridged. During the oven and sintering process, the temperature rises too fast, and the moisture in the charge material will rapidly form a large number of micropores on the furnace wall. These micropores may cause the penetration of the molten metal and the adsorption of the slag. Therefore, the development and strict adherence to the furnace operating procedures is the primary condition for improving the service life of the lining.
2. The increase in the capacity of the induction furnace and the reduction of the thickness of the furnace wall will affect the service life
As the capacity increases, the static pressure of the furnace wall with the molten metal increases. The pressure at the junction of the hearth and the furnace wall is the largest, and it is also a place where problems are more likely to occur. As the static pressure increases, the probability of penetration of the molten metal into the micropores or microcracks of the furnace wall also increases; the electromagnetic stirring force also increases, and the flushing effect on the furnace wall is also enhanced. Some units blindly pursue over-loading and reduce the thickness of the furnace wall, especially for larger electric furnaces, and the life of the lining will be significantly reduced. Choosing a lining material suitable for a large-capacity electric furnace and achieving a reasonable wall thickness can improve its use.
3. Melting Temperature
If the temperature of the molten metal is too high, the erosion of the slag on the lining will be intensified; the fluidity of the molten metal will increase and penetrate into the crack, which will intensify the chemical attack of the molten metal on the lining. High-temperature tapping and low-temperature casting have always been the operating guidelines. However, each type of casting has its melting process requirements. When it reaches the appropriate temperature, do not pursue excessive over-temperature, and always observe and measure temperature. While trying to control the excessively high melting temperature, do not have a long-term high temperature or heat preservation waiting for casting. Excessive temperature will not only cause the alloy to burn, but also damage the furnace wall, and the energy consumption will also increase.
4. The Influence of the Smelting Material
The furnace lining just finished, the furnace wall has not been completely sintered, the first few furnaces should use relatively clean metal materials, try to avoid complex materials, materials containing more rust and oil, especially oil leaching Iron filings. A material with a low melting point and good fluidity will intensify the penetration of the furnace wall; a material with a high melting point requires a higher temperature. These have the life of the lining and should be arranged to be suitable for melting in the middle and late stages. In addition, different materials should be smelted to pay attention to the properties of metal materials. As in the case of a furnace with high sulfur content, the next furnace smelting high manganese steel is very likely to cause erosion of the furnace wall. The composition is complex, contains more rust, oil, no cleaned waste, and the complexed intercalation between the oxides formed at high temperatures and high oxygen, which is easy to form sticky slag and erode the furnace wall. The wall appears loose and melted. The impurities brought in not only increase the energy consumption but also affect the quality of the casting.
5. The impact of the smelting operation: the melting period of the metal charge can be melted a lot.
The tightness of the charge is directly related to the melting rate of the charge. In order to heat and melt quickly, the charging should be tight, but it must be avoided during the melting process; bridging; phenomenon, which will overheat the molten metal in the lower part, so that the molten metal will inhale and increase the burning of alloying elements. Prolong the melting time, high temperature and severe eddy current will seriously erode the furnace wall, appear; bridge; and treatment; bridging; damage to the furnace wall is very large. When the metal level is too low, pay special attention to the feeding. If the large block is added and the electric furnace inputs high power, the bottom will cause severe overheating to exacerbate the erosion. The whole lining has the highest static pressure in the middle and lower parts, and the highest temperature, scouring The most serious. After the molten metal liquid reaches the appropriate temperature and quality requirements, it should be powered off, which not only makes it safe and reduces energy consumption but also protects the lower half of the lining from damage due to overheating molten metal. Minimize the smelting time and reduce the electricity consumption of molten steel.
6. Influence of slag on the erosion of the furnace wall: The pH of the slag should be compatible with the material of the lining material.
The magnesia lining material has a strong resistance to alkali slag erosion; the siliceous acid lining material has strong acid slag resistance; the alumina neutral lining material exhibits typical bisexuality in different pH at high temperature, which can be adapted Slag with different pH, but slightly worse than acid charge and alkaline charge. The metal material added to the furnace will bring in various oxides, and the slag composition of different materials and different heats will be different. Most of the various oxides, carbides, sulfides and various compound compounds present in the slag will chemically react with the lining to form new compounds with different melting points. The melting points of some low melting point oxides such as fayalite (FeOSiO2) and manganite (MnOSiO2) formed in the reaction are generally in the range of about 1200 °C. The low melting point slag has excellent fluidity, may form a fluxing agent, and produces a severe chemical attack on the lining, thereby reducing the service life of the lining. The high melting point slag formed in the reaction, such as mullite (3Al2O3 ● 2SiO2), forsterite (2MgO ● SiO2), etc., and some high melting point metal elements having a melting point of up to 1800 ° C or higher, high melting point slag suspended in the molten metal There is a relatively complicated interpenetrating solution between the low melting point slag and the slag. The slag is easily adhered to the furnace wall and accumulates, causing serious slag, affecting the power, melting speed and capacity of the electric furnace until the lining life is affected.
In such a situation, the following measures can be taken to eliminate:
(1) Strengthening the management of incoming materials: drastically reducing the materials with sand, rust and oil stains, and the waste materials containing various impurities and the returning materials are important measures to prevent the erosion and sticking of the induction furnace lining.
(2) Formulating a suitable process: According to the material of the furnace lining and the alloy to be melted, the order of addition and the appropriate melting process are established, and the opportunity and time for minimizing the contact between the impurities and the lining are also effective methods for preventing the slag of the induction furnace.
(3) Use new auxiliary materials to clean oxides and impurities in molten metal and slag: For example, deoxidation uses a multi-element composite deoxidizer instead of a single element deoxidizer. The single element deoxidizer deoxidation product has a higher melting point, exists as a solid particle in the molten metal, is difficult to discharge, and is easy to adhere to the furnace wall, while the rare earth element, as a deoxidizer, has strong deoxidation ability, but its deoxidation product density It is also difficult to remove from the molten metal, and the rare earth element is easily chemically reacted with SiO2 and Al2O3 in the siliceous and alumina lining materials to erode the furnace wall. The multi-element composite deoxidizer such as silicon aluminum strontium has strong deoxidation ability, and the product after deoxidation is a liquid particle, which is easy to float and remove. A variety of slag compounds in the molten metal and a variety of harmful gases, if not completely removed, not only cause the slag of the lining, but also cause various casting defects in the casting, and the high-quality slag remover can The surface scum is cleaned, but impurities and gases that are miscible and suspended in the molten metal cannot be removed. In this case, the use of steel (iron) water cleaner can effectively solve the problem. Steel (iron) water cleaner is a composite material suitable for use in materials such as ductile iron, gray iron, carbon steel, alloy steel, high manganese steel, and stainless steel. The oxide in the steel (iron) water can be quickly reduced and removed, the molten steel is purified, and the viscosity of the molten steel is significantly lowered to improve the fluidity. During the smelting process, the steel (iron) water cleaning agent can effectively soften the slag, prevent the non-melting oxide from adhering to the furnace wall, thereby improving the energy efficiency, shortening the smelting time, and effectively removing the slag adhered to the lining, thereby improving induction furnace lining life.
All in all, the life of the induction furnace lining material is three minutes in the material and seven points in use. Effectively improve the life of the lining material, in addition to selecting the appropriate material of the lining material, the implementation of strict furnace baking process, the development of a scientific and rational smelting process, the use of new auxiliary materials and meticulous operation, careful maintenance and other work are improved The life of the lining is an effective way to achieve energy saving.
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